Conventionally, there is known a plasma generation device that generates electromagnetic wave plasma by emitting electromagnetic waves to a combustion chamber of an internal combustion engine. For example, Japanese Unexamined Patent Application, Publication No. 2009-36200 discloses a plasma generation device of this kind.
More particularly, Japanese Unexamined Patent Application, Publication No. 2009-36200 discloses an internal combustion engine in which microwave plasma is generated by way of microwaves. In the internal combustion engine, discharge plasma formed by a discharge electrode of a spark plug is irradiated with electromagnetic waves from an electromagnetic wave radiator (antenna), and the discharge plasma grows and expands. The internal combustion engine is an internal EGR (Exhaust Gas Recirculation) type internal combustion engine, in which residual gas components are subject to a plasma process immediately before intake stroke.